<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      #d1 {
        width: 100px;
        height: 100px;
        border: 1px solid red;
        margin-left: 100px;
        margin-top: 100px;
        margin-bottom: 50px;
        margin: 50px;
        margin: 50px 100px;
        margin: 0 auto;
        margin: 10px 20px 30px 40px;
      }

      #d2 {
        width: 100px;
        height: 100px;
        border: 1px solid red;
        margin-top: 50px;
      }

      span {
        border: 1px solid blue;
      }

      #s1 {
        margin-right: 50px;
        /* 行内元素上下外边距无效 */
        margin-top: 50px;
      }

      #s2 {
        /* 左右相邻彼此添加外边距，两者相加，上下相邻取最大值 */
        margin-left: 50px;
      }

      #big {
        width: 200px;
        height: 200px;
        background-color: red;
        /* 解决子元素粘连问题 */
        overflow: hidden;
      }

      #big > div {
        width: 50px;
        height: 50px;
        background-color: green;
        margin-left: 100px;
        /* 当元素的上边缘和上级元素的上边缘重叠时，给元素添加上外边距会出现粘连显示异常，给上级元素添加overflow:hidden解决 */
        margin-top: 100px;
      }
    </style>
  </head>

  <body>
    <div id="big">
      <div></div>
    </div>
    <span id="s1">span1</span><span id="s2">span2</span>
    <div id="d1"></div>
    <div id="d2"></div>
  </body>
</html>
